Los Angeles County Sheriff's Department deputies investigating a "suspicious package" outside the world's largest water treatment plant in Carson on Tuesday morning discovered it was only a discarded stereo speaker.

Deputies saw the "package" during a precautionary sweep of the Joint Water Pollution Control Plant at about 7:45 a.m. at 24501 S. Figueroa Street in southwestern Carson, on the border of Wilmington. The sweep was part of a series of searches in response to the Boston bombing. Members of the sheriff's Arson and Explosives Detail responded and determined that it was not a bomb several hours after it was found, officials said.

The plant is one of the largest of its kind in the world, according the Sanitation Districts of Los Angeles County's website. It serves roughly 3.5 million people in Los Angeles County, treating about 280 million gallons of wastewater per day and releasing it to the Pacific Ocean.